A “multispectral” imaging system can be defined as an imaging system that collects images from two to fifteen or so spectral bands. These bands range from about 400 to 2500 nanometers in the electromagnetic spectrum. In the physical world, this range of wavelengths represents a spectral “window” in the atmosphere where sunlight passes through and strikes the earth. A “band” is a portion of this spectrum with a given spectral width, such as 10 or 50 nm. Other imaging systems are referred to as “hyperspectral”, and collect images from dozens to hundreds of spectral bands, usually narrower than those collected by multispectral imaging systems.
Examples of multispectral and hyperspectral imaging systems are airborne or satellite-based imaging systems that collect images representing light reflected from the earth. These systems are also often referred to as multispectral or hyperspectral remote sensing systems.
The availability of multispectral and hyperspectral imaging systems has provided the designers of imaging systems the ability to select from among a wide variety of sensors and sensor combinations. Electro-optical (EO) imaging devices such as color (RGB) and monochromatic cameras are able to produce a two dimensional array of information similar to that projected onto the human retina. Other imaging devices, such as infrared (IR) cameras and passive millimeter wave (PMMW) sensors, are able to operate at wavelengths outside the human visible spectrum, thereby being able to differentiate objects from the background based on other characteristics such as thermal gradients. Other sensors such as LADAR (laser radar) add another dimension of information by providing range as well as reflectance data.
It is also possible to derive images from the “primary” images collected by various sensors. For example, images representing characteristics such as hue, saturation, and texture can be derived from RGB images. These derived images can also be useful in analyzing a particular scene.
Depending on the desired application of a particular imaging system, the images from one combination of sensors is likely to be more useful than another. There exists a need for a method to facilitate evaluating the effectiveness of various combinations of sensors.